How Airbags Work

Posted by Auto Surgeons on Oct 22, 2017

An airbag is more correctly known as a supplementary restraint system (SRS) or supplementary inflatable restraint (SIR). The word "supplementary" here means that the airbag is designed to help the seatbelts protect you rather than replace them. Hence, relying on an airbag to protect you without fastening your seatbelt is extremely dangerous.

Like the trusty seat belts, the concept of the airbag -- a soft pillow to land against in a crash -- has been around for many years. The first patent on an inflatable crash-landing device for airplanes was filed during World War II. In the 1980s, the first commercial airbags appeared in automobiles.

How Airbags Work

When a car hits something, it starts to decelerate very rapidly.

An accelerometer (electronic chip that measures acceleration or force) detects the change of speed.

If the deceleration is great enough, the accelerometer triggers the airbag circuit. Normal braking doesn't generate enough force to do this.

The airbag circuit passes an electric current through a heating element(a bit like one of the wires in a toaster).

The heating element ignites a chemical explosive. Older airbags used sodium azide as their explosive; newer ones use different chemicals.

As the explosive burns, it generates a massive amount of harmless gas (typically either nitrogen or argon) that floods into a nylon bag packed behind the steering wheel.

As the bag expands, it blows the plastic cover off the steering wheel and inflates in front of the driver. The bag is coated with a chalky substance such as talcum powder to help it unwrap smoothly.

The driver (moving forward because of the impact) pushes against the bag. This makes the bag deflate as the gas it contains escapes through small holes around its edges. By the time the car stops, the bag should have completely deflated.

How effective are airbags?

To date, statistics show that airbags reduce the risk of dying in a direct frontal crash by about 30 percent (30%) but it's important to note that airbags are violently explosive and present dangers of their own. The biggest risk is to young children, though adults also face a small risk of eye injury and hearing loss. If an airbag saves your life, you probably consider a slight risk of injury a price well worth paying. Even so, it's clearly important to study the potential dangers of airbags so we can make them as safe and effective as possible.

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